The present invention relates to electronic circuits for domestic electrical appliances, the main field of use of the invention being that of washing machines. This invention relates in particular to an electronic card equipped with a controller for three-phase asynchronous motor or a chopper for universal motor.
The types of electric motor recently used in this field, such as three-phase asynchronous motors, require a more complex control than the universal electric motors or single-phase asynchronous motors conventionally used in domestic electrical appliances. Normally, an electronic card separate from that of the programmer is used, dedicated to this new motor control requirement, which raises complex problems of interfacing the two electronic cards and the need to be able to modify and adapt these electronic cards significantly for them to communicate.
In order to overcome these drawbacks, a choice can be made to combine the two programmer and motor control functions on one and the same electronic card, which can, because in this case only one card is used instead of two, be a way of reducing the corresponding costs and simplifying the power supply.
However, the two programmer and motor control functions cannot be referenced to the sane potentials. In practice, the electronic programmer card is normally referenced to the neutral potential to be able to control the load control triacs, whereas the motor control card is placed after a rectifying diode bridge and is therefore referenced to the neutral potential but also to the phase, alternately.
To make these two programmer and motor control functions communicate, it is therefore necessary to electrically insulate the communication. There is also a need for a microcontroller for each of these two functions and referenced to the reference of the function. More particularly, the programmer microcontroller must be referenced to the neutral potential, whereas the motor control microcontroller is referenced to the “zero” potential of the rectifying diode bridge, each microcontroller having a separate power supply.
In order to overcome these constraints, it has already been proposed to move the optical communication insulation, so that the two functions are referenced to the same potential.
Based on this principle, a known solution consists in referencing these two functions to the neutral potential. In this case, it is necessary to place the optical insulation in the power part of the motor control function. However, the optical insulation is more restrictive when it comes to the motor control power, because the frequencies of the signals are high (from 16 to 24 kHz) and the delays induced by the insulation must be low. This is why the components capable of providing this function are expensive. Furthermore, given that the control power part of the motor is insulated from the microcontroller, the latter cannot directly perform, on the control power part of the motor, the current or voltage measurements necessary for the control function. This solution is therefore costly and is not suitable for all motor control contexts.